Concentrated developers



United States Patent G CONCENTRATED DEVELOPERS Richard W. Henn,Rochester, N. Y., assignor to Eastman Kodak Company, Rochester, N. Y., acorporation of New Jersey No Drawing. Application July 28, 1953, SerialNo. 370,867

4 Claims. (Cl. 96-66) This invention relates to photographic developersand more particularly to concentrated photographic developers andmethods for their preparation.

Photographic developers are frequently prepared in a concentrated formto increase the convenience of storage and shipping. The concentrate maybe a mixed powder comprising the solid ingredients of the formula. Forconvenience in preparing the working solution, however, and tofacilitate making small volumes of working solution, the concentrate isfrequently prepared in liquid form. Unfortunately, the ordinarycomponents of a developer have a limited solubility and it is uncommonto be able to concentrate the working strength developer by more thantwo or three times. The use of solvents, and of especially solubledeveloping agents allows rather higher concentration, but the limits aresoon reached. In some cases an excess of the salts or developing agentshas been left in the developer in the form of a slurry, but this has notproven satisfactory, as the salts settle out and form larger aggregateswhich are very diificult to dissolve.

Still another attempt to produce concentrated developers has led to thepreparation of pastes in which the components are suspended in suchmaterials as glycerine, a dextrose solution, or a viscous amine. Thesehave never proven satisfactory due to a separation of the salts from theliquid and to the slow solubility of the components.

It is an object of the present invention, therefore, to provide a moresuitable method of preparing concentrated photographic developers. It isanother object to prepare concentrates of particularly low bulk. It is afurther object to prepare concentrates which are readily dispersible inwater. Yet another object of the invention is to provide a concentrateddeveloper in which the solid developer constituents are held in auniform suspension in a colloid comprising alginic acid, salts ofalginic acid or esters of alginic acid from which they will dissolverapidly to form the developing solution. Other objects will becomeapparent from the description.

In accordance with the invention, these objects are attained bysuspending the finely ground components of the developer in a highlysoluble gel. Colloids suitable for this suspension are found in alginicacid (a. polymer of anhydro-fl-d-mannuronic acid) its salts and esters.These are available commercially under such trade names as Kelacid,Kelgin, Kelcoloid, Superloid, etc. These compounds are highlyhydrophilic, and their gels show high salt tolerance and dispersereadily on addition of more water to the gel. This is in sharpdistinction to the characteristics shown by other commonly usedhydrophilic colloids, such as karaya, locust bean gum, tragacanth,acacia, and the like. The invention therefore comprises the suspensionof the finely divided solid components of the photographic developer ina gel made with an appropriate concentration of such a compound ofalginic acid as is mentioned above. The

I 2,784,086 Patented Mar. 5 1957 concentration needed will depend onboth the nature of the developer and the viscosity of the selectedcolloid, but will lie between V2 and 10% and more commonly between 1 and5%. The invention is further illus trated in the following examples:

Example 1.-A universal developer The individual components of thisdeveloper were first ground to pass through an mesh sieve. They werethen added successively to ml. of a 2% solution of Kelgin (sodiumderivative of algin).

Grams Sodium sulfite 24.0 Sodium carbonate 45.0 Elon (monomethylp-aminophenol sulfate) 1.6 Hydnoquinone 4 .8 Potassium bromidee 1.0Sodium tetraphosphate 2.0

Example 2.Vqrious colloids In preparing a developer of the abovecomposition and by the above procedure, the following colloids werefound suitable:

7 Percent Kelcosol, high viscosity sodium derivative of algin- 0.5Kelcoloid, low viscosity propylene glycol derivative of alg Kelgin,medium viscosity sodium derivative of algin- Kelgin XL, extra lowviscosity sodium derivative of alnin 5 Kelacid, alginic acid 2 Example3.Mixing procedure In the procedure of Example 1 the finely groundingredients were added successively to a solution of the gel. Thisresults in almost immediate setting of the gel. Alternative procedureswhich may be employed include:

(a) The developer ingredients are completely mixed. A suitablepreservative, such as phthalic anhydride may be added. They are thenfinely ground, and added to the gel solution. In the case of the formulaof Example 1, stirring for 15 minutes was necessary before gelationoccurred and a permanent suspension was produced.

(b) The developer components are ground in water, rather than dry, andthe gel is added from a thicker solution. In the case of the formula ofExample 1, 48 cc. of water were employed and 28 cc. of a 2% solution ofKelgin. The mixture set rapidly.

(c) The powders are ground directly in the gel. Again using the formulaof Example 1, setting was found to occur rapidly if the powders wereadded successively in the order named, grinding after each addition, butif added as a mixed unit, and then ground, the slurry required stirringfor 90 minutes before setting occurred.

Example 4.-Negative developer The following ingredients, ground to passa 60-mesh sieve, were added successively to 30 cc. of a 2% solution ofsodium alginate, The sodium alginate employed was the Kelgin" ofExamples 1 and 3.

Grams Sodium sulfi "19.2 Sodium "rnetaborate, -otahydrate 614 Elon-(monomethyl 'p-taminophenol sulfate 116 Hydroquinone 1.6 Potassiumbromide 0.3

This yielded a permanent gel of moderate viscosity which was found to bereadily dispersible in water. Used in the proportion of 1 part of :gelto '15 :PaItS'Of water it produced a developer'entirely suitable:for-the processing of high speed negative emulsions.

was added to 400 cc. of a 2% solution of Kelgin and 100 cc. of water andball milled-for "20 hours. The resulting suspension dissolved rapidly inwater, to produce a developer suitable for X-ray materials when dilutedin the proportions of 1 part of gel to 15 parts of Water.

As indicated above Kelg in is a medium viscosity so dium alginate;Kelcoloid is a propylene glycol derivative of algin; Kelcosol is a highviscosity sodium alginate; and Superloid is a high viscosity ammoniumalginate.

The particular advantage of the present invention is that when theconcentrate is diluted to form the working developer, it does not have aviscosity appreciably greater than the same developer without thecolloid. The sole purpose of the alginate is to hold the solid developerconstituents in a uniform suspension from which they will dissolverapidly to form the working solution.

I claim:

1. A photographic developer comprising a silver halide developer and analkali both of which are in finely ground solid form suspended as athick paste in a colloidal gel consisting of a compound selected fromthe group consisting-of alginic acid, a salt of 'al'ginic acid, and anester of alginic acid, said compound *being in to 40% concentration inWater.

2. A photographic developer comprising a silver halide developer and analkali both of which are in finely ground solid form suspended as athick paste in a colloidal gel consisting of sodium alginate colloid,said colloid being in /2% to 10% concentration in Water.

3. A photographic developer comprising monomethyl p-aminophenol sulfate,hydroquinone, potassium bromide, sodium sulfite, sodium carbonate, andsodium tetraphosphate all of which are in finely ground solid formsuspended as a thick paste in a colloidal gel consisting of sodiumalginate colloid, said colloid bein'g in /2'% to 10% concentration 'inwater.

"4.- A photographic developer comprising monomethyl p-aminophenolsulfate, hydroquinone, potassium bromide, sodium s'ulfit'e, sodiumcarbonate, sodium tetraphosphate and phthalic anhydr-ide all of whichare in finely ground solid form suspended as a thick paste "in acolloidal gel consisting of sodium alginate colloid, said colloid beingin to 10% concentration in water.

References oitedinthe fileof this patent UNITED STATES PATENTS

1. A PHOTOGRAPHIC DEVELOPER COMPRISING A SILVER HALIDE DEVELOPER AND ANALKALI BOTH OF WHICH ARE IN FINELY GROUND SOLID FORM SUSPENDED AS ATHICK PASTE IN A COLLOIDAL GEL CONSISTING OF A COMPOUND SELECTED FROMTHE GROUP CONSISTING OF ALGINIC ACID, A SALT OF ALGINIC ACID, AND ANESTER OF ALGINIC ACID, AND COMPOUND BEING IN 1/2% TO 10% CONCENTRATIONIN WATER.